Some observers say a failure of U.S. intelligence allowed terrorists to mount the bold attacks on New York and Washington. But national security analysts say there is little -- if anything -- that even a well-prepared country can do to keep terrorists from its borders. Our correspondent Andrew F. Tully reports.

Washington, 15 September 2001 (RFE/RL) -- National security analysts say the terrorists who carried out Tuesday's attacks in New York and Washington used time-tested, low-tech methods to elude discovery by the world's most sophisticated military, intelligence and law enforcement systems.

These methods seldom produce quick results -- sometimes it takes years to plan and execute an attack -- but they are extremely reliable, according to the analysts. And one of them told RFE/RL that there is essentially nothing the U.S. or any other country can do to stop them.

Since the beginning of espionage, governments have relied on spies who gather information themselves or recruit agents to betray their governments or organizations. And many governments -- particularly the U.S. government -- have also gathered intelligence with high-technology electronics to intercept their enemies' sensitive communications.

But analysts interviewed by RFE/RL say these methods often do not work with terrorists because of the very structure of their networks. One is Celeste Wallander, the director of the Russia and Eurasia Program at the Center for Strategic and International Studies, a private policy institute in Washington. She says that during the 20th century, many revolutionary or terrorist groups have been structured on the model pioneered by Bolsheviks during the Russian Revolution.

Wallander describes the model this way: Each cell is made up of three people. One of those people knows one member of another three-member cell. Another member of this second cell knows one member of a third cell, and so forth, making up a tightly woven network of operatives.

"So it was very hard to unravel, because it's not as if anyone else knew not only who they were but what they were doing -- you know, the coordination would come only through that one link."

Wallander says this structure makes each individual in a cell dispensable if he is caught.

The Red Army Faction in Germany operated roughly along the lines of the Leninist cell model, according to Wallander. She says that German security services were able to identify several members of the group, but could not break up the entire network because of its structure.

Some analysts, however, say terrorists cannot help using some of the technology that is at virtually everyone's disposal. Jack Spencer, a defense and national security analyst with the Heritage Foundation, an independent policy center in Washington, told RFE/RL that he believes the people behind the American attacks must have used some modern communications technology without detection. For instance, he said, there are many ways for a determined person to remain anonymous while sending messages on the Internet.

Spencer also agrees that it is virtually impossible for U.S. agents to penetrate terrorist cells, especially in the Middle East. But he stresses that there are old-fashioned, low-tech ways of gathering fragments of information and fitting them together as if they were pieces of a jigsaw puzzle.

"Because these cells are hard to infiltrate, and maybe sometimes impossible, they don't operate in a vacuum. People know about them at some level."

"I'm making it sound very simple, but the essence of simplicity is extreme complexity -- a great deal of planning and, as one person put it, a great deal of money had to be generated."

According to Pitorri, America is virtually helpless to prevent such an assault, no matter how efficient its intelligence, its military, its law enforcement.

This does not mean that many planned terrorist acts in America have not been stopped. But Pitorri says these, too, were prevented not so much with computers and other high-tech gadgets, but with careful surveillance, another reliably low-tech method.